Scientists at the University of California, Riverside, have created a new type of ultra-thin film that has incredible ability to change color when twisted or bent. The researchers believe such materials could one day appear on robots, giving them chameleon-like skin, or turning them into cash as a means of verifying their authenticity.
The new film functions like some of the discolored materials we’ve studied in the past, involving charged particles that change color as light changes, and very fine ridgelines that reflect light at different wavelengths when they are distorted or bent. The same team created an early iteration of the film in 2014, which changes color under pressure as a way to monitor mechanical pressure.
But according to the team, the latest version is different from previous versions of these films because it can be programmed to show unique complex patterns. The team achieved this by making tiny rod-shaped films of gold nanoparticles, which appear different colors depending on their size, shape and orientation.
“In our case, we reduced gold to nano-sized rods, ” says Yan Yadong, a chemistry professor. “We know that if we can point the bars in a particular direction, we can control their color. Facing one direction, they may appear red. By moving 45 degrees, they will turn green. “
To get millions of of these gold nanorods to face in the same way, the team first fused them with smaller rods and encapsulated them in polymer shields, locking them side by side and letting their orientation be determined by the magnets. “It’s like you’re holding a magnet on a bunch of needles and they all point in the same direction. “Yu Yadong said. “That’s how we control color. “
The researchers then dried the nanorods onto the film, where they were locked in their direction. “However, if the film is flexible, you can bend and rotate it, and as the direction changes, you will still see different colors. Professor Gong explained. According to the researchers, the film can be applied to the surface of an object, as easy as painting on the house, which gives us some interesting potential. It can be used in robots to change color according to changes in the environment, or as a currency certification technology. They even think of futuristic art as a possibility.
“Artists can use this technology to create fascinating paintings that can vary greatly depending on the angle of view. The researchers said. “It would be great to see the beauty of science and art in our work.” “
The study was published in the journal Nature-Communications.